The invention relates to a method for controlling the flying height of the magnetic head in a magnetic storage unit, and to an apparatus for performing this method.
Magnetic head assemblies that fly relative to magnetic storage media have been used extensively, particularly in disk files where the head assembly is attached to an actuator which moves the heads generally radially to access different concentric data tracks on the disk. The objectives for improving the non-contact transducing relationship between a magnetic head and a magnetic recording medium, such as a rotary disk, are to attain very close spacing between the head and the surface of the recording medium, and to maintain the attained spacing essentially constant. The head/surface spacing, usually called `flying height` is one of the parameters which determine the maximum possible storage density. Other important parameters include the narrowness of the transducing gap and the thickness of the magnetic recording medium. Small flying height allows for high spatial frequency signals to be recorded, thereby affording high density recording. Additionally, by having a reduced flying height, regulated to a constant value, the amplitude of the signal being recorded or read out is thus improving signal resolution and making signal processing more reliable.
Traditionally, the flying of a magnetic head over the surface of a moving recording medium is regulated passively by adjusting the aerodynamic properties of the medium/head assembly, i.e. surface geometry, distance and velocity of relative displacement. While many known magnetic storage units rely on the air cushion that builds up naturally with disk rotation and relative displacement, other storage units use a forced air cushion generated by pressurized air exiting from a plurality of openings on the surface of the head facing the magnetic recording medium. With this air bearing technology flying heights down to about 300 nm having been achieved. However, further reduction of the flying height appears difficult with this technology.
The state of the art of magnetic recording on moving media is perhaps still best documented in R. E. Matik, Computer Storage Systems and Technology, John Wiley & Sons, N.Y., 1977, p. 342 ff.